A general procedure for studying single cell secretion will be used to examine single cells that produce antigen-specific suppressor factors and lymphotoxin. This procedure will also be applied to a study of the mechanism of antibody production; in particular, a reported process of DNA excretion by antigen-stimulated lymphocytes will be examined. The objectives of these experiments include an unambiguous determination of the functional properties of immunocompetent cells by studying single cells rather than purified subpopulations. A knowledge of the functional properties of immunocompetent cells is necessary for an orderly dissection of the immune response and changes that might occur in autoimmune and neoplastic disease.